OK, here's my ideal trip, if I was heading north from San Francisco and wanting to do a loop through Vancouver BC. I would want a variety of scenery, and as the OP said, shorter drive times. Understand that you will hit traffic congestion on I-5 north or southbound between Chehalis WA and Eugene OR. This is the main route for large truck traffic and combined with urban sprawl makes for a less than interesting view point.
Heading north on the coast road up to the Redwoods - visit the state park and the National Park. Sleep in Arcata or Crescent City - check out the bay at Crescent City.
Continue north on 101 to Bandon and Reedsport - plenty of places to stop and view, and to stay over. The Oregon Dunes are magnificent.
Fire up the GPS, and head east on one of the state highways. Aim for Eugene. Nice places to stay, a university town (lots of wineries to check out along the way).
Head east from Eugene towards Newberry Oregon and visit the volcano there. Head north towards Redmond Oregon. Along the way visit the High Desert Museum in Bend.
High Desert Museum: highdesertmuseum.org There are plenty of places to stay in Redmond.
By now you've seen beaches, forests, and dry vistas of eastern Oregon. Continue north on I-97 to the Dalles and cross the Columbia River into Washington. Then depending on your likes, either:
Head west on Washington 14. Stop by a Stonehenge replica dedicated to WWI veterans, then onto to Maryhill Museum (about 3 miles), then onto Maryhill Winery (nice restaurant too!). And then further west to I-5. Northbound, stop at Mt. St. Helens (again plenty of places in the I-5 corrider to pull off and stay). Continue north using recommendations from others here about Seattle and northward (including west across the Sound to Olympic National Park, or east from Tacoma to Mt. Rainier, and or east from Sedro Wooley to the North Cascades National Park).
or
Continue north on I-97 through the Yakima Valley observing the high desert. Once in the Yakima area there are many wineries to visit if that is what you like. Also good places to stay and marvelous views of Mt. St. Helens, Mt. Adams, and Mt. Rainier.
Continue north to Ellensberg and on to Wenatchee. Head west at Highway 2 to the Bavarian town of Leavenworth. Great walking, shopping, eating, sleeping. Continue west to I-5 and then north to Vancouver.
Return: Vancouver to Victoria. Victoria via Ferry to Pt Angeles, then onto the Olympic National Park. West out of Pt Angeles to Forks and south along 101 all the way to Astoria. Continue down the Oregon/California coast, or move east onto I-5 for a faster drive home.
BTW, I think this is more than 2 weeks, but it gets you out of the I-5 corridor to the eastern parts of Oregon and Washingon. In eastern Oregon you also get great views of the the large and small volcanoes in the Cascade Mountains.
-- Rita